/Engine/Source/Runtime/Slate/Public/Widgets/Input/SSubMenuHandler.h
Returns whether or the sub-menu entry should appear hovered. If the sub-menu is open we will always show the menu as hovered to indicate which sub-menu is open In the case that the user is interacting in this menu we do not show the menu as hovered because we need to show what the user is actually selecting
bool ShouldSubMenuAppearHovered() const